In biochemistry fields, technique using a microreactor for e.g., separation, synthesis, extraction or analysis of a minuscule quantity of reagents have been recently attracting attention. The microreactor is composed of a microchip having a small substrate composed of e.g., silicon, a silicone resin or glass on which a channel for analysis at a micro scale is formed by a semiconductor micro fabricating technique.
A reaction analysis system using such a microreactor is referred to as a micro total analysis system (hereinafter called “μTAS”). The μTAS provides effects such as the increase in a ratio of a surface area to a volume of reagents, and therefore enables a reaction analysis at a high speed with high precision leading to the provision of a compact and automated system.
Allowing the microchip to include a flow path called a microchannel which has regions exerting various functions, such as a reaction region having a reagent placed thereon, makes it possible to form microchips employable in various applications, the applications including analysis in the fields of chemistry, biochemistry, pharmacy, medical science and veterinary science, such as genetic analysis, clinical diagnosis and drug screening, synthesis of compounds and environmental measurements.
Such microchips have a typical structure in which a pair of substrates facing each other are bonded to each other, with the surface of at least one of the substrates having a microchannel (approximately measuring, e.g., from ten to several hundred micrometers in width, from ten to several hundred micrometers in depth). A substrate for forming the microchips used in most cases is a glass substrate, which is readily producible and allows for optical detection. Also, recent years have seen the ongoing development of microchips made of a resin substrate, which is lightweight, more unlikely to break than the glass substrate, and is inexpensive.
Conceivably, processes for laminating substrates together in the production of microchips involve the use of an adhesive or the use of heat sealing, and yet these processes have problems as follows.
Problems with the lamination process using an adhesive include the adhesive's exuding into the microchannels thereby clogging the microchannels or narrowing part of the microchannels, consequently causing the channels to have a non-uniform diameter; and disordering homogenous properties of wall surfaces of the channels.
Problems with the lamination process using heat sealing include the crushing of channels during a heating stage caused by the sealing carried out at a temperature exceeding heat melting temperature, and the failure of channels to retain a predetermined cross-sectional shape, which would lead to the difficulty in giving the microchip higher functions.
In view of the above circumstances, a method proposed recently is the application of vacuum ultraviolet ray onto the surface of the substrates thereby activating the surface of the substrates, and then laminating the resultant substrates together (see Patent Literatures 1 to 5).